Which is the correct lewis dot structure of c2h2

The correct answer is A

The octet rule state that all main group elements form bonds such that they achieve a noble gas configuration with eight valence electrons. In this case carbon has 4 electrons in its outermost shell  and requires 4 more electrons to achieve an octet. Hydrogen is an exception to the octet rule and it only requires two electrons to achieve an octet. All the other options have C and H  forming bonds that do not lead to a noble gas configuration.

it should have an internal chamber and two thermometers sticking out of the top. the internal chamber will also be closed off from the outside.